1. FIELD OF THE INVENTION
This invention concerns catalysts and methods for the activation or regeneration of catalysts for use in Ni-catalyzed hydrocyanation processes.
2. TECHNICAL REVIEW
U.S. Pat. Nos. 3,496,215, 3,496,217, 3,496,218, 3,655,723 and U.S. Pat. No. 3,798,256, which are incorporated herein by reference, describe alkene hydrocyanation in the presence of low valent, organophosphorus Ni complexes and, in some cases, Lewis acid promoters.
U.S. Pat. No. 4,394,321, which is incorporated herein by reference, discloses the preparation of Ni(NCR).sub.4 (NCBAr.sub.3).sub.2 complexes, where Ar is an aryl radical, hereinafter referred to as NCBC's. In large-scale, BAr.sub.3 -promoted hydrocyanation processes, quantities of deactivated catalyst, primarily NCBC's and Ni(CN).sub.2, accumulate.
U.S. Pat. No. 3,859,327, which is incorporated herein by reference, describes the regeneration of active, zerovalent Ni catalyst by treating degraded catalyst with finely divided reducing metals and, optionally, a zinc halide promoter in a 60.degree.-40.degree. C. temperature range. Two disadvantages of this process are the relatively high temperatures required and the moderate yields of regenerated catalyst obtained (23-59%) in the absence of zinc halide promoter. While zinc halide promoters significantly improve the yield of regenerated catalyst, the zinc halide promoters are incompatible with BAr.sub.3 -promoted hydrocyanations because, as disclosed in U.S. Pat. No. 4,874,884, they have different inherent promoter characteristics and so represent potential new deleterious contaminants to the hydrocyanation process.
U.S. Pat. No. 3,655,723, cited above, describes the synthesis, but not the regeneration of Ni catalyst from MBH.sub.4 and various Ni complexes including Ni(CN).sub.2. This procedure suffers from the inherent reactivity of byproduct boranes with alkenes, particularly pentenenitriles. This type of borane reactivity with alkenes is disclosed in U.S. Pat. No. 3,798,256 and is well documented by H. C. Brown in Organic Synthesis Via Boranes, John Wiley & Sons, New York, 1975. Again, these by-product boron compounds have different promoter characteristics than the BAr.sub.3 promoters.
It is an object of the present invention to regenerate high yields of valuable Ni catalyst from degraded catalyst under mild conditions without the production of deleterious contaminants, using reagents that produce only byproducts which are compatible with BR.sub.3 (R is an organic radical of up to 18 carbon atoms) promoted hydrocyanations.